[cloud-init] "/etc/resolv.conf" is out of control of netconfig after done cloud-init GOSC on SLES15SP1

[Cuixiang Zhang]

[cloud-init] "/etc/resolv.conf" is out of control of netconfig after done cloud-init GOSC on SLES15SP1

Before GOSC, "/etc/resolv.conf" is link file "/run/netconfig/resolv.conf", in control by netconfig. After done cloud-init GOSC, this file become real file not link file, total different from "/run/netconfig/resolv.conf".

cloud-init version is 19.4.
```
pek2-gosv-16-dhcp83:~ # cloud-init -v
/usr/bin/cloud-init 19.4
```

Before GOSC:
```
pek2-gosv-16-dhcp83:~ # ll /etc/resolv.conf
lrwxrwxrwx 1 root root 26 Feb 10 23:33 /etc/resolv.conf -> /run/netconfig/resolv.conf
```

After GOSC:
```
pek2-gosv-16-dhcp83:~ # ll /etc/resolv.conf
-rw-r--r-- 1 root root 153 Feb 11 09:46 /etc/resolv.conf
pek2-gosv-16-dhcp83:~ # ll /run/netconfig/resolv.conf
-rw-r--r-- 1 root root 707 Feb 14 06:10 /run/netconfig/resolv.conf

```

cloud-init.log is attached.

Steps:
1. Deploy SLES15SP1 VM
2. Power off VM and Deploy GOSC
```
2020-02-11 08:46:34,797 - config_file.py[DEBUG]: FOUND CATEGORY = 'NETWORK'
2020-02-11 08:46:34,797 - config_file.py[DEBUG]: ADDED KEY-VAL :: 'NETWORK|NETWORKING' = 'yes'
2020-02-11 08:46:34,797 - config_file.py[DEBUG]: ADDED KEY-VAL :: 'NETWORK|BOOTPROTO' = 'dhcp'
2020-02-11 08:46:34,797 - config_file.py[DEBUG]: ADDED KEY-VAL :: 'NETWORK|HOSTNAME' = 'gosc-dhcp-vm-01'
2020-02-11 08:46:34,797 - config_file.py[DEBUG]: ADDED KEY-VAL :: 'NETWORK|DOMAINNAME' = 'eng.vmware.com'
...

```
3. Power on VM and check GOSC resolve, expect /etc/resolv.conf is still link to /run/netconfig/resolv.conf and DNS setting is saved into this file.

[Pengpeng Sun (pengpengs)]

Found on VMware platform, loaded DatasourceOVF.
VMware internal bug number is: 2508900

[Dan Watkins (oddbloke)]

Thanks for using cloud-init and for taking the time to file this bug! Could you run `cloud-init collect-logs` on an affected instance and attach the tarball it produces to this bug, please? Once you've done that, please move it back to New.

Thanks!

Dan

[Cuixiang Zhang (cuixiangz)]

full cloud-init log is attached.

BRs,
Cuixiang Zhang

[Ryan Harper (raharper)]

Hi,

Thanks for the logs. cloud-init does not currently render network config on SuSE in such a way that integrates with netconfig from SuSE. Some background and discussion happened in this bug, in particular this comment:

https://bugs.launchpad.net/cloud-init/+bug/1843634/comments/9

At this time, if you specify static DNS configuration in cloud-init's network-config, cloud-init will create a resolv.conf with the expected values from the config and will effectively disable netconf management of resolv.conf.

[Xiaofeng Wang (xiaofengw)]

Hi Ryan,
Is there any plan to write the settings into netconfig file: /etc/sysconfig/network/config?

[Dan Watkins (oddbloke)]

This isn't currently queued for implementation by the Canonical cloud-init team, but we would happily accept contributions that addressed it.

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/3606